/* Copyright (C) 2016-2018 Alibaba Group Holding Limited

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#include "murmurhash.h"

namespace ps {

namespace {

inline uint64_t rotl64(uint64_t x, int8_t r) {
  return (x << r) | (x >> (64 - r));
}

inline uint64_t fmix64(uint64_t k) {
  k ^= k >> 33;
  k *= 0xff51afd7ed558ccdULL;
  k ^= k >> 33;
  k *= 0xc4ceb9fe1a85ec53ULL;
  k ^= k >> 33;

  return k;
}

}  // namespace

// smhasher implementation:
// https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
void MurmurHash::operator()(const void* key, const int len, void* out) {
  const uint8_t* data = (const uint8_t*)(key);
  const int nblocks = len / 16;

  uint64_t h1 = seed_, h2 = seed_;

  const uint64_t c1 = 0x87c37b91114253d5ULL;
  const uint64_t c2 = 0x4cf5ad432745937fULL;

  const uint64_t* blocks = (const uint64_t*)(data);
  for (int i = 0; i < nblocks; ++i) {
    uint64_t k1 = blocks[i*2];
    uint64_t k2 = blocks[i*2+1];

    k1 *= c1; k1 = rotl64(k1, 31); k1 *= c2; h1 ^= k1;

    h1 = rotl64(h1, 27); h1 += h2; h1 = h1*5+0x52dce729;

    k2 *= c2; k2 = rotl64(k2, 33); k2 *= c1; h2 ^= k2;

    h2 = rotl64(h2, 31); h2 += h1; h2 = h2*5+0x38495ab5;
  }

  const uint8_t* tail = (const uint8_t*)(data + nblocks*16);

  uint64_t k1 = 0, k2 = 0;
  switch(len & 15) {
    case 15: k2 ^= ((uint64_t)tail[14]) << 48;
    case 14: k2 ^= ((uint64_t)tail[13]) << 40;
    case 13: k2 ^= ((uint64_t)tail[12]) << 32;
    case 12: k2 ^= ((uint64_t)tail[11]) << 24;
    case 11: k2 ^= ((uint64_t)tail[10]) << 16;
    case 10: k2 ^= ((uint64_t)tail[9]) << 8;
    case 9: k2 ^= ((uint64_t)tail[8]) << 0;
            k2 *= c2; k2 = rotl64(k2, 33); k2 *= c1; h2 ^= k2;
    case 8: k1 ^= ((uint64_t)tail[7]) << 56;
    case 7: k1 ^= ((uint64_t)tail[6]) << 48;
    case 6: k1 ^= ((uint64_t)tail[5]) << 40;
    case 5: k1 ^= ((uint64_t)tail[4]) << 32;
    case 4: k1 ^= ((uint64_t)tail[3]) << 24;
    case 3: k1 ^= ((uint64_t)tail[2]) << 16;
    case 2: k1 ^= ((uint64_t)tail[1]) << 8;
    case 1: k1 ^= ((uint64_t)tail[0]) << 0;
            k1 *= c1; k1 = rotl64(k1, 31); k1 *= c2; h1 ^= k1;
  }

  h1 ^= len; h2 ^= len;
  h1 += h2;
  h2 += h1;

  h1 = fmix64(h1);
  h2 = fmix64(h2);

  h1 += h2;
  h2 += h1;

  ((uint64_t*)out)[0] = h1;
  ((uint64_t*)out)[1] = h2;
}

}  // namespace ps
